Image Visualization Accelerator Device Description

This section describes behavior that is specific to HCRX devices with Image Visualization Accelerator (IVX) hardware. See the "HCRX Family Device Descriptions" section for general information on these devices. Note that IVX is supported on the HCRX-8 and HCRX-24 devices. IVX is not supported on the HCRX-8Z, VISUALIZE-8, HCRX-24Z, and VISUALIZE-24 devices.

Device Description

IVX accelerates many image processing operations in IVL. IVX is an accelerator that provides hardware support for the following:

Input data formatting
Convolution (with 3×3 kernel)
Pan and zoom
Rotations
Bicubic interpolation
Bilinear interpolation
Nearest-neighbor interpolation
Window-level mapping
Rasterization
Window clipping
Scissor operations

Angle of Rotation

The angle of rotation is limited to increments of 0.1 degrees. You can supply any value, but it may be modified for rendering. For example, an angle of 23.89 degrees will be modified to 23.9 degrees for rendering. The angle of 23.89 degrees will be maintained by the API state, even though it renders at 23.9 degrees.

Rasterization

IVX rasterizes image data into the frame buffer from the bottom to the top of a window, and left to right across a scan line. This differs from other HP raster graphics devices, which rasterize from the top to the bottom of a window. The bottom-to-top order matches the semantics of the OpenGL API.

Performance Hints

Clip Rectangles

The performance of IVX will degrade as four or more clip rectangles obscure your image. This can be caused by software-specified clip boundaries or overlapping windows. If these conditions exist, multiple passes will be required to draw the same image.

Software versus Hardware-Accelerated Paths

As previously mentioned, HCRX devices with IVX hardware will use the accelerated hardware implementation of IVL whenever possible. The following conditions will force these devices to use the unaccelerated software path instead:

If post-convolution bias is used.
If the convolution kernel coefficient is 16.0 or greater.
If the scale factor is outside the range of positive or negative 1.0 to 32.0, inclusive.
For rotation angles that are not a multiple of 90 degrees, the absolute value of the ratio of the x zoom factor and the y zoom factor must be less than 2:1. In other words, the following condition should hold: 0.5\leq|\hbox{\it zoom}_x|/|\hbox{\it zoom}_y|\leq 2.0.
The image size must be between 8×4 (width×height) pixels and 32768×32768 pixels, inclusive.
If your input format is GL_RGBA in a depth-24 visual, the hardware path will only be used if convolution is disabled and window-level mapping is not used.

Also, only drawing operations use the hardware path. Read and copy operations use the software path.

Image Visualization Accelerator Device Description

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